Melt-processible conducting polymer blends based on fibrils of intractable conducting poymers

ABSTRACT

Microfibrils are formed which include conductive conjugated polymer. These microfibrils are incorporated into polymer admixtures which are thermo-formed into conductive shaped articles.

This application is a divisional of application Ser. No. 08/099,629,filed Jul. 30, 1993, now U.S. Pat. No. 5,427,855 which was in turn adivisional of application Ser. No. 07/697,316 filed May 6, 1991 and nowU.S. Pat. No. 5,246,627.

FIELD OF THE INVENTION

This invention relates generally to conducting polymers, and moreparticularly to melt-processible conducting polymer blends based onfibrils (i.e. fine conducting "needles" with length much greater thandiameter) of the conducting polymer component blended with common,commercial insulating polymers so as to obtain shaped articles (forexample by injection molding, film extrusion, etc.) which are conductiveat low volume fractions of the conducting polymer component and whichexhibit excellent mechanical properties.

BACKGROUND OF THE INVENTION

With the discovery of conducting polymers in the late 1970's, thepossibility of combining the important electronic and optical propertiesof semiconductors and metals with the attractive mechanical propertiesand processing advantages of polymers was proposed. Without exception,however, the initial conducting polymer systems were insoluble,intractable, and non-melting (and thus not processible) with relativelypoor mechanical properties.

Success in developing a number of processing routes has opened the wayto fabricating conductive polymers into fibers and films etc; i.e. intoshapes that can be used for a wide variety of potential applications inthe electrical industry. Important problems remain to be solved beforesuch materials can be put into wide spread use. Among these are cost,environmental stability, and melt processibility:

(1) In many cases the starting materials and the synthesis of conjugatedpolymers are (at least currently) expensive.

(2) Although a number of conjugated polymers have been developed whichappear to be stable, long term stability in different environments isstill an important problem.

(3) The development of melt processible conducting polymer systems wouldopen a large market for such materials.

One important route toward solution of these problems is to utilizeblends and/or composites of conducting polymers with conventional (meltprocessible) polymers. The dilution of the expensive conjugated polymerin a relatively low cost host (such as, for example polyethylene)immediately yields a major cost benefit. At the same time, such blendseffectively encapsulate the conductive polymer fraction within theenvironmentally stable host, leading to greatly improved long termstability. The achievement of melt-processibility of conductive polymersremains as an important unsolved problem.

There are a large number of melt-processible polymers many of which arecommercially available. Today, most melt-processible polymers (such aspolyolefins, polyesters, nylons, etc.) with useful mechanical propertiesare insulators. It would clearly be desirable to render such materialsconducting. Previous attempts to render such materials conducting haveutilized the general method of filling them with a volume fraction ofconducting material such as particles of carbon black, or metal flakesor particles (for example, silver flakes). Addition of such fillers atsufficiently high quantity to yield connected conducting paths (i.e. tobe above the percolation threshold; for example, typically about 16% byvolume for globular particles) yields moderate electricalconductivities, but at the expense of the mechanical properties. Thetensile strength and elongation at break are severely reduced by thefillers. Moreover, because of the sharp onset (known as the "percolationthreshold") of the electrical conductivity as a function of the volumefraction of the filler in such conventionally filled polymers, it isdifficult to fabricate articles of moderate electrical conductivity(e.g. less than 10⁻⁴ S/cm) for a variety of uses which include thedissipation of static charge. The same disadvantages (e.g. the existenceof a sharp threshold for conductivity of the blends at about 16% volumefraction of the conducting polymer, etc.) are relevant to usingconducting polymers as filler (see, for example, Conducting PolymerComposites of Soluble Polythiophenes in Polystyrene by S. Hotta, S. D.D. V. Rughooputh and A. J. Heeger, Syn. Mtls. 22(1):79 (1987); andreferences therein).

Alternatively, reticulate doped polymers (J. K. Kreska, J. Ulanski, andM. Kryszewski, Nature, 298:390 (1981)) are composites with a crystallineadditive organized into different structures; i.e. isotropic 3- or2-dimensional dendritic networks (J. Ulanski, A. Tracz and M.Kryszewski, J. Phys. D: Appl. Phys. 18:L167 (1985); J. K. Jezka, A.Tracz, J. Ulanski and M. Kryszewski, Pol. Pat. No. 138,395 (1985)),quasi-one-dimensional highly oriented crystalline `strings` (L. Burda,A. Gracz, T. Pakula, J. Ulanski, and M. Kryszewski J. Phys. D: Appl.Phys. 16:1737 (1983); J. Ulanski, A. Tracz, E. El Shafee, G. Debrue andR. Deltour, Synth. Met. 35:221 (1990)), or chaorically dispersed,separated needles or dendrites [M. Kryszewski, J. K. Jeszka, J. Unanskiand A. Tracz, Pure and Applied Chemistry, 56:355 (1984)). Miscellaneousconducting reticulate doped polymers have been obtained using variouspolymer matrices and various conducting charge-transfer complexes (seeJ. Ulanski, A. Tracz, J. K. Kreszka and M. Kryszewski, Mol. Cryst. Liq.Cryst. 118:443 (1985)). However, the reticulate doped polymers areobtained by solution casting of films from a common solution of polymerand the charge transfer salt additive in such conditions that duringfilm solidification, the additive crystallizes in situ (under controlledconditions) in the polymer matrix. Although these reticulate dopedpolymer composite systems exhibit a low percolation threshold andrelatively high conductivity, they are not melt-processible.

Thus, the ability to melt-process conducting articles from polymers andthereby to fabricate such conductive polymers by injection molding, filmextrusion etc. into shaped articles with excellent mechanical propertiesremains seriously limited.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to overcome theaforementioned disadvantages of the prior art and, primarily, to providemelt-processible composites/blends of conjugated polymers with common,commercial insulating polymers, said composites/blends beingelectrically conductive and exhibiting excellent mechanical properties.

It is additionally an object of the present invention to providemelt-processible composites/blends of common, commercial insulatingpolymers with conjugated polymers, said conjugated polymers being in theform of fibrils or fine conducting "needles" with length much greaterthan diameter.

It is additionally an object of the present invention to provide methodsfor the fabrication of fibrils of various conductive polymers withaspect ratios of more than 10 and with a diameter on the micron- orsubmicron scale.

It is still another object of the invention to provide fibrils ofconducting polymers which are intractable, but stable (at least for therelatively short times sufficient to accomplish the melt-processing) attemperatures suitable for melt-processing common, commercial insulatingpolymers.

It is a further object of this invention to provide melt-processibleblends/composites of conducting high-aspect ratio fibrils (such as thosemade from polyaniline or composites of polyaniline with nylons, aramids,and the like) in melt-processible conjugated polymer hosts, such as forexample the poly(3-alkylthiophenes), P3AT's. Since typically suchconjugated polymers have finite conductivity without doping, thecomposite/blend will exhibit electrical conductivity controlled by thevolume fraction of the added fibrils at any volume fraction; i.e. therewill be essentially no percolation threshold.

Additional objects, advantages and novel features of the invention willbe set forth in part in the description which follows, and in part willbecome apparent to those skilled in the art on examination of thefollowing, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and attained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

We have now found that these objects can be accomplished by a new methodfor producing shaped electrically conductive articles. This methodinvolves producing conducting polymer-containing fibrils asintermediates and then incorporating the fibrils into a mixture withheat processible polymer and forming the shaped article from the mixtureunder conditions which substantially retain the fibrils' physical form.

Thus, in one aspect, this invention provides this process for formingconductive shaped articles. In a further aspect, it provides the shapedarticles formed using fibrils as intermediates. In another aspect, itprovides the fibril intermediates, whether made directly from aconductive polymer or a conductive polymer blend or from a conjugatedpolymer or conjugated polymer blend which is subsequently rendered moreconductive by doping or the like. In yet an additional aspect, thisinvention provides the methods of forming the conductive polymerfibrils.

DETAILED DESCRIPTION OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS

In this specification, reference will be made to the Drawings in which:

FIG. 1 is a graph showing conductivity data (from Table 2 and Table 3)for microfibril materials as a function of PANi content. In these datathe solid points are PANi/nylon-6 microfibers and the open circles arePANI/PPTA microfibers.

FIG. 2 is a graph showing conductivity data for PTV/PE films fabricatedfrom microfibril materials as a function of PPTV content of themicrofibrils (from Table 5). In the figure--solid points are materialsdoped with iodine vapor and open circles are materials doped with FeCl₃.

FIG. 3 is a graph showing conductivity data for PTV/PE-FeCl₃ filmsfabricated from microfiber material as a function of PPTV content (fromTable 8).

FIG. 4 is a graph showing conductivity data for blends of PTV/PE-FeCl₃film fabricated from microfiber material with PE as a function of PPTVcontent (from Table 10).

FIG. 5 is a graph showing conductivity data for blends of PTV/PE-FeCl₃microfibers with PE as a function of PPTV content (from Table 11).

DESCRIPTION OF PREFERRED EMBODIMENTS

This section contains the following subsections:

The Microfibrils

The present invention employs elongate fine microfibrils of conjugatedpolymer. These materials are fine needles. Typically, they have a lengthwhich is greater than their diameter. This ratio of length/diameter isreferred to as an "aspect ratio." Commonly, the fibrils have an aspectratio of at least 5, preferably at least 10, and more preferably atleast 50, such as from about 50 to about 250.

These microfibrils preferably have diameters of less than about 200 μm.(The use of the word "diameter" is chosen to define the average radialcross-dimension. While the fibrils may have a circular cross section,the use of the word "diameter" is not to imply that they must have sucha shape. Usually, the finer the fibril diameter, the better, withdiameters of less than 50 μm being preferred and fibrils with diametersof 10 or even 1 μm or less being more preferred.

The microfibrils contain conjugated polymer. They can be a homopolymerof conjugated polymer or they can be a blend of conjugated polymer andnon-conjugated fibril-forming polymer. The fibrils can be conducting asformed or they can be formed in a low conductivity state and renderedmorehighly conducting by positive or negative doping.

The conjugated polymer can be selected from the conjugated-conductivepolymer-forming polymers known in the art. These include poly(aniline)andsubstituted poly(aniline), such as poly(lower(C₁ -C₄)alkyl anilines).The poly(anilines) can exist in a protonated (H⁺) state orthey can existas non-protonated bases such as the emeraldine base or as salts such asalakali metal salts. Most commonly, the poly(anilines) are employed asprotonated forms of commercially available emeraldine base.

Other representative conjugated polymers include poly(pyrrole) andpolymersof derivatives of pyrrole such as poly(alkoxypyrroles) and poly(alkylpyrroles). Poly(para-phenylene sulfide) can be used as well, ascan poly(phenylenevinylene) ("PPV") and C₁ -C₁₀ alkoxy derivatives ofpoly(phenylenevinylene) such aspoly(2,5-dimethoxy-p-phenylenevinylene)("PDMPV"), poly(2-methoxy,5-(2'-ethylhexyloxy)-p-phenylenevinylene) ("MEH-PPV"), andthe like; poly(thienylenevinylenes) ("PTV") such aspoly(2,5-thienylenevinylene) and alkoxy and alkyl derivatives thereof;andpoly(thiophene) and the "P3AT's" or poly(3-alkyl(C₆ -C₁₆)thiophenes)such as poly(3-hexyl, 3-octyl, 3-nonyl, 3-dodecyl or3-hexadecylthiophene). These polymers can have degrees of polymerization whichresult in average molecular weights ranging anywhere from about 1,000daltons to 10⁶ daltons polymer is not considered critical. Rather, anypolymer having conjugated unsaturated bonds in its repeat units, such asthe materials just set forth, so as to be able to stabilizeconductingdopants and the like and thus give rise to conductive polymers can beused.

The conjugated polymer can be employed as a homopolymer in themicrofibrilsor it can be present as an admixture with one or morenon-conductive, non-conjugated (saturated) carrier polymer. Theselection of carrier polymer should be made from polymers which aresoluble in solutions of theconjugated polymer and capable of formingfibrils when precipitated from these solutions together with theconjugated polymer. Additionally, they should preferably be materialsthat are thermally stable at the temperatures subsequently used toheat-process the product into the final shaped articles so as to helpretain the fibril configuration during this final shaping.

Additional criteria for the selection of the carrier polymer are asfollows: the material should allow for the formation of mechanicallycoherent fibrils and remain stable in solvents that are capable ofdispersing or dissolving the conjugated polymers prior to precipitatingand forming the fibrils. Selection of the carrier polymer is madeprimarily on the basis of this compatibility with the conjugated polymeras well as with the solvent or solvents employed. For example, blendingofpolar conjugated polymers generally requires carrier polymers that arecapable of codissolving with or absorbing polar reactants. Examples ofsuch materials are poly(vinylalcohol), poly(ethyleneoxide),poly(para-phenylene terephthalate), poly(para-benzamide) and the like.On the other hand, if the blending of the conjugated polymer and thecarrier can proceed in a non-polar environment, non-polar carrierstructures may be selected such as those containing poly(ethylene),poly(propylene), poly(butylene), poly(vinylchloride) and the like.

Using the selection criteria, the carrier polymer may be selected frompolymers such as polyamides, such as nylon 6, nylon 6.6, nylon 4.6,nylon 11 and nylon 12; polyesters such as poly(ethylene terephthalate),poly(butylene terephthalate), poly(paraphenylene terephthalate),polyolefins, such as poly(ethylene) or poly(propylene) or poly(butylene)and copolymers of these olefins with other materials such as propylene,butylene, haptene, hexene and octene; vinyl polymers, such aspoly(styrene), poly(vinylchloride), poly(vinylalcohol) and copolymers ofstyrene with butadiene, acrylonitrile or acrylates.

Turning now to the issue of relative concentrations of the conjugatedand carrier polymers, it will be noted that one can use homopolymers ofthe conjugated material, i.e., 100% conjugated material. It has alsobeen found, however, that one can obtain the desired conjugated polymerproperties when the fibrils contain only a minor fraction of conjugatedpolymer. Thus, the relative proportions of conjugated material tocarrier polymer can range down to about 1 part conjugated material toabout 250 parts non-conjugated carrier polymer. As will be demonstratedherein in the examples, the electrical conductivity which results is adirect function of the fraction of conductive polymer present. Thus,depending upon the application desired, the proportion of conductivepolymer can be varied throughout this range. Usually, the relativeproportions of conjugated:carrier polymers range from 10:1 to about1:30.

The conductivity of the material also depends upon whether or not itcontains dopants. The conjugated polymers themselves offer somemeasurablelevels of conductivity without dopants. Dopants increase theconductivity significantly as demonstrated in the examples. Thesematerials which can include electron-accepting and electron-donatingsubstances may be presentin concentrations ranging from 0.001% to 50%molar based on the number of conjugated units present in the conjugatedpolymers. Typical dopants include FeCl₃, PF₆ ⁻, SbF₆ ⁻, etc. and/ordispersable elements such as I₂, and acids, such as in H₂ SO₄, CH₃ HSO₃,HCl, etc.

Microfibril Preparation

The above-described microfibrils can be prepared by precipitating theconjugated polymer together with any carrier polymer from liquidsolution under vigorous agitation. (By the terms "vigorous agitation,""turbulent mixing" or the like is meant a degree of agitation or mixingwhich gives rise to a Reynold's number in the mixed liquid greater than3,000 and preferably greater than 3,500.

The microfibrils can be formed by the use of precipitation induced bychilling or by the use of non-solvents. For example, a solution of theconjugated polymer and optional carrier polymer can be added to avigorously agitated chilled liquid, for example, aqueous ice slurry, orchilled non-solvent. Alternatively or coincidentally, the solution ofconjugated polymer and optional carrier polymer can be added to anon-solvent for these materials. Thus, if the conjugated polymer issoluble in and coming out of a polar solution, such as an aqueoussolution, it could be added to a material such as an organic liquid inwhich the conjugated polymer is not substantially soluble. Irrespectiveofthe exact precipitation method employed, thermal, non-solvent, or thelike,it is important that the precipitation be carried out undervigorous agitation.

Thus, in this process, if a highly polar conjugated polymer is used, itmayrequire a very polar solvent such as water or the like as its solventphase. Less polar materials may employ alcohols, ketones, ethers, loweramides, and the like as solvents with appropriately chosen non-solvents.

Following precipitation, the microfibers can be doped, if desired, suchas by adding FeCl₃ or iodine or the like. These materials may be addedduring precipitation or may be added after precipitation. Themicrofibrilsformed by precipitation are recovered by filtration or thelike.

Microfibril Admixtures and their Preparation

The microfibrils prepared as described above are employed as componentsof heat-processible polymer admixtures. These admixtures include themicrofibrils just described and a suitable non-conductive insulatingpolymer. The polymers employed as the non-conductive insulating polymersmay be selected generally from the materials described above as carrierpolymers. Preferably, however, the materials selected for this use areheat-processible at lower temperatures than the temperatures at whichthe carrier polymers would melt or degrade. This allows the microfibrilsto retain, to a substantial extent, their integrity during thesubsequent heat processing. This factor should be kept in mind whenselecting a carrier polymer and insulative polymer for the sameadmixture system. The proportion of insulative polymer and microfibrilsmay be selected over a broad range depending upon the electricalproperties desired in the final shaped articles. For example, theproportions may range from about 99.9 parts microfibrils to 0.1 partsinsulative polymer to the converse, i.e., 0.1 parts microfibrils to 99.9parts of the insulative polymer. In most applications, however, there isgenerally a more significant fraction of each material. Thus, preferredratios run from about 99 parts of one material to 1 part of the other tothe converse. Even more preferred are materials where there is between 9parts of fibril to 1 part of insulativepolymer to from 1 part of fibrilsto 9 parts of insulative polymer.

The preparation of these materials generally proceeds though thephysical mixing of the microfibrils with the insulative polymer, theinsulative polymer being in a finely divided, i.e., powdered or chopped,form. These materials are thoroughly mixed to give a finely dividedmaterial which canthen be heat-processed to form the final shapedarticle.

Forming Shaped Articles

The above-described powdered admixtures of fibrils and insulativepolymer are heat-formed into shaped articles. By shaped articles ismeant any material having at least one formed dimension such as sheets,rods, extrudates, spun fibers, cast materials, molded materials and thelike. Inall of these applications, the mixed materials are subjected toheat and/orpressure to an extent adequate to permit the individualparticles to fuse together and form a solid shaped article. Typicalconditions include temperatures ranging from about 100° C. to about 500°C. andespecially about 100° C. to about 350° C. and pressures rangingfrom 0 psi up to several thousand psi. These conditions should beselected typically as the mildest conditions possible for processing themixed material into the desired solid objects so as to minimizedegradation of the microfibrils. The above-described temperatures aremerely representative and those of skill in the processing of polymersinto finished articles will be able to select exact conditions whichservetheir desired purposes.

Representative Applications

The shaped articles which can be produced by the process of thisinvention have a number of unique and desirable properties. For one,they can have asignificant conductivity. This can allow them to work asantistatic fibers,antistatic films, antistatic coatings, and the like.These materials can also be used as electromagnetic interference (EMI)shields. They can be conducting or semi-conducting materials as thoseterms are used in the art. This can give rise to semiconducting andconducting papers, felts, nonwoven fabrics, woven fabrics, cloths, andthe like. The ability to control the electrical properties of thepolymer using this process gives rise to the ability also to tailor anyof the aforementioned products to particular electrical or electronicproperties, if desired. In addition, these materials can be used inelectronic applications as components of semiconductors, conductors, andthe like.

This invention will be further described by the following Examples.These are provided to illustrate the invention and are not intended tolimit itsscope which is defined by the appended claims.

Examples Example 1

Commercially available nylon 6 (1.945 g) was added to 17.51 gconcentrated sulfuric acid (97%). A homogeneous 10%(w/w) nylon6/sulfuric acid solutionwas obtained. Polyaniline (1 g of the emeraldinebase) was dissolved in 49 g of 97% sulfuric acid to prepare a 2%polyaniline solution. 5.0 g of the 10% nylon 6/sulfuric solution and8.34 g of the 2% polyaniline solution were mixed together and 0.73 g of97% sulfuric acid was added to keep the total solid content in solutionat 3.5%(w/w). The solution was stirred to make it homogeneous. Ice (3Oz) and water (9 Oz) were mixed in a blender and stirred for 2 min toobtain a dilute ice slurry. The PANi/nylon 6/H₂ SO₄ solution was addedslowly under vigorous stirring (1800rpm in the blender) over a period of2 min and then stirred (again vigorously) for an additional 2 min. Theresulting microfiber material wasfiltered and treated with 200 ml of 1Maq. HCl solution for 6 hours. The fully-protonated microfibers werefiltered again and washed several times subsequently by methanol,acetone and benzene and then transferred into vacuum flask. The flaskwas cooled by an ice bath for 30 min to allow the benzene to solidify.The flask was then connected to a vacuum line and thesolid benzene wassublimated by evacuation (<10⁻³ torr) during 24 hours. Part of resultingsponge like PANi/nylon 6 was pressed into a pellet for conductivitymeasurements. The typical length to diameter ratiofor 1/3 (w/w)PANi/nylon 6 fibrils was 50-100 as determined by optical microscopyobservation. This value changes with relative ratio of PANi andnylon 6in initial solution and also with the speed and duration of stirring.Table 1 gives typical data of diameter and length to diameter ratio formicrofibers of different composition obtained at same conditionsofstirring as described previously.

                  TABLE 1                                                         ______________________________________                                        Typical Dimensions of the PANi/nylon-6                                        Microfibers                                                                                  microfiber                                                                              aspect ratio                                         PANi/nylon 6   diameter  (length to                                           ratio          (μm)   diameter)                                            ______________________________________                                        0.00           10-20      50-100                                              0.33           10-20      50-100                                              0.50           15-50     15-30                                                1.00           flakes with occasional fibers                                  ______________________________________                                    

To change the PANi/nylon 6 ratio in the microfiber, the amount of nylonsolution (10 g) and total solids content (3.5%) were kept unchangedthroughout the experiment; the amount of 2% polyaniline solution andpure sulfuric acid added were varied.

Table 2 gives the conductivity data (obtained from four-probemeasurements)for microfibers with different compositions. The data ofTable 2 are also shown in graphic form in FIG. 1.

                  TABLE 2                                                         ______________________________________                                        Conductivity of PANi/nylon-6 Microfiber Material                              PANi/nylon 6 ratio (w/w)                                                                       Conductivity (S/cm)                                          ______________________________________                                        0.030            6 × 10.sup.-4                                          0.100            0.19                                                         0.333            1.12                                                         0.500            0.63                                                         1.000            2.10                                                         ______________________________________                                    

Example 2

The experiment in Example 1 was repeated except that the resultingmicrofiber material was treated by 1.0M aq. H₂ SO₄ instead HCl. Theelectrical conductivity for the 1/3 (w/w) PANi/nylon 6 microfiber was0.23 S/cm.

Example 3

The experiment in Example 1 was repeated except that to thePANi/nylon-6/H₂ SO₄, the equivalent amount (two aniline to onep-sulfonic styrene ring) of poly-p-sulfonic styrene was added, and themicrofibers were not treated by 1.0M HCl after microfiber formation. Theelectrical conductivity for 1/3 (w/w) PANi/nylon-6 fiber was 1.1×10⁻²S/cm. Therm gravimetric analysis data demonstrated that the thermalstability was greatly enhanced by using this polymer protonation agent.

Example 4

Poly(para-phenylene terephthalamide), PPTA, (1.5 g) was dissolved in98.5 gconcentrated sulfuric acid (97%) to prepare a 1.5% PPTA/H₂ SO₄solution. PANi/H₂ SO₄ solution (2%) was prepared as describedinExample 1. To prepare 1/3 (w/w) PANi/PPTA/H₂ SO₄ solution, 12.53 g of1.5% PPTA/H₂ SO₄ solution, 3.13 g of 2% PANi/H₂ SO₄ solution and 4.34 gof 97 H₂ SO₄ were mixed together and stirred. The total solid content inthe solution was 1.25%. The procedure for microfiber formation wasessentially the same as described in Example 1. The only difference wasthat the total solids content was kept constant (1.25%) for all thedifferent PANi/PPTA ratios. From opticalmicroscope observations, thelength to diameter ratio of the microfibers was more inhomogeneous forPANi/PPTA (than for the PANi/nylon 6 microfibers) and ranged frommicrofibers with aspect ratios of about 10-30to some thin flakes. Thisis also consistent with the lower conductivity observed for PANi/PPTAmicrofibers in comparison with that for PANi/nylon 6 microfibers. Theconductivity data of pressed pellets of PANi/PPTA are given in Table 3.The data of Table 3 are also plotted in FIG. 1 to enabledirectcomparison of the conductivity results for PANi/nylon 6 and PANi/PPTAmicrofibers.

                  TABLE 3                                                         ______________________________________                                        Electrical conductivity of PANi/PPTA microfibers                              PANi/PPTA ratio (w/w)                                                                          Conductivity (S/cm)                                          ______________________________________                                        0.01             5.3 × 10.sup.-7                                        0.03             8.0 × 10.sup.-6                                        0.10             6.0 × 10.sup.-5                                        0.33             1.1 × 10.sup.-2                                        0.50             2.4 × 10.sup.-2                                        1.00             4.9 × 10.sup.-1                                        ______________________________________                                    

Example 5

The emeraldine base (EB) form of polyaniline (1 g) was dissolved in 100g N-methyl pyrrolidinone (NMP). The insoluble part was filtered and thesoluble part was concentrated (by evaporation) to a 2% solution.Polyvinylchloride (PVC, M_(w) =110,000, Polyscience Inc.), 15 g, wasdissolved in 85 g NMP to obtain a 15% (w/w) solution. The EB/NMPsolution (0.3 g) was mixed with 2 g of the 15% PVC/NMP solution andstirred overnight to obtain a homogeneous solution. The resultingPANi/PVC/NMP solution was slowly added into 200 ml of methanol inblender while stirring vigorously. Examination of the material under anoptical microscope indicated formation of microfibers with diameter ofabout 1 μm and with a length to diameter ratio of greater than 50.Microfibers were filtered and put into 100 ml of 1M aq. HCl solution forprotonation. The resulting fully protonated microfibers were separatedby filtration and dried under dynamic vacuum. The typical conductivitydata are shown inTable 4.

                  TABLE 4                                                         ______________________________________                                        Electrical conductivity of PANi/PVC microfibers                               PANi/PVC (w/w)  Conductivity (S/cm)                                           ______________________________________                                        0.0033          1.3 × 10.sup.-7                                         0.0098          1.2 × 10.sup.-7                                         0.0196          2.7 × 10.sup.-6                                         ______________________________________                                    

Example 6

Different weighed quantities of the precursor polymer, PPTV, ofpoly(thienylene vinylene), PTV, were dissolved in 20 g of1,2,4-trichlorobenzene (TCB) at room temperature. In each case,ultra-highmolecular weight polyethylene, UHMW PE, (0.02 g) was added atapproximately150° C. A clear, transparent, light yellow solution wasobtained after stirring at 150° C. for 10 to 20 minutes. Subsequently, asmall amount of hydrochloric acid (0.035-0.070 g) was introduced intothe solution to effect a conversion of PPTV to PTV. The solution wasstirred at temperatures between 150°-160° C. for 10 minutes. Theresulting solution was semi-transparent with a pink to black color;darkerin rough proportion to the amount of PPTV added in the initialstep. The solution was precipitated in EtOH (95%) under vigorousstirring in a blender for 5-7 minutes. The precipitate of PTV/PEmicrofibers was filtered and washed with acetone, and then dried invacuum at room temperature. The diameter of the microfibers was about 3μm, the lengthto diameter ratio was around 12. The microfibers could bepressed into a thin sheet; the resulting sheet was flexible with a colorwhich ranged from pink to black; again, the color was darker in roughproportion to theamount of PPTV added in the initial step. Thinner filmsof the PTV/PE microfiber blend were obtained by hot-pressing themicrofiber sheet at 160° C. for 2-3 minutes. Iodine-doping was effectedat a pressure of about 1 mm Hg of I ₂ vapor. FeCl₃ doping was achievedby allowing the sample to come to equilibrium in 0.1M solution ofnitromethane.

The electrical conductivity of the PTV/PE films is given in Table 5 andplotted graphically in FIG. 2.

                  TABLE 5                                                         ______________________________________                                        Electrical conductivity of PTV/PE Films                                       PPTV Content *  Conductivity (S/cm)                                           (%)             I.sub.2 -doping                                                                         FeCl.sub.3 -doping                                  ______________________________________                                        4.8             8.3 × 10.sup.-7                                                                   2.4 × 10.sup.-9                               9.1             8.3 × 10.sup.-5                                                                   4.8 × 10.sup.-9                               11.1            --        1.1 × 10.sup.-8                               14.3            --        3.6 × 10.sup.-3                               20.0            1.0       2.2 × 10.sup.-2                               33.3            8.4       3.0 × 10.sup.-2                               50.0            13.5      3.4 × 10.sup.-2                               66.7            11.5      --                                                  100             80        47.8                                                ______________________________________                                        * PPTV content = W.sub.PPTV / (W.sub.PPTV + W.sub.PE).                    

The mechanical properties of the PTV/PE films as summarized in Table 6

                  TABLE 6                                                         ______________________________________                                        Mechanical Properties of PTV /PE Films                                        PPTV Content                                                                             Young's Modulus                                                                             Tenacity  Elongation                                 (%)        (GPa)         (GPa)     (%)                                        ______________________________________                                        0          0.37          0.15      270                                        4.8        0.52          0.18      228                                        9.1        0.59          0.22      258                                        20.0       0.60          --        149                                        33.3       0.63          --        166                                        50.0       0.63          0.29      266                                        ______________________________________                                    

Example 7

Conductive PTV/PE--FeCl₃ microfiber material (i.e. conducting withoutsubsequent doping) was obtained by precipitating PTV/PE/TCB solution(prepared as in Example 6) in FeCl₃ --CH₃ NO₂ under vigorous stirring ina commercial blender for 5-7 minutes. The precipitate, in the form ofPTV/PE--FeCl₃ microfibers, was washed with CH₃ NO₂ and dried in vacuumat room temperature. The diameter of the microfibers was about 3 μm, thetypical length to diameter ratio was around 12. After pressing themicrofibers into a sheet,the structure was flexible with a color of pinkto black depending on PPTV content. At the same PPTV content, the colorof PTV/PE--FeCl₃ microfibers was darker than that of the correspondingPTV/PE microfibers.

PTV/PE--FeCl₃ films were obtained by hot-pressing the microfibers at160° C. for 2-3 minutes. It was found that the concentration of FeCl₃--CH₃ NO₂ had a major effect on the electrical conductivity of thecomposite (Table 7).

The electrical conductivity of the PTV/PE--FeCl₃ films is given in Table8 as a function of the PPTV content. The data of Table 8 areplottedgraphically in FIG. 3. The mechanical properties of thePTV/PE--FeCl₃ films are summarized in Table 9.

Surprisingly, the conductivity of the PTV/PE--FeCl₃ films was found tobestable upon heating; the conductivity of the films decreased by onlyoneorder of magnitude after the material was pressed at 160° C. for 7minutes.

                  TABLE 7                                                         ______________________________________                                        The Effect of FeCl.sub.3 Concentration on the                                 Conductivity of PTV/PE--FeCl.sub.3 *                                          Concentration of FeCl.sub.3                                                                     Conductivity                                                (M)               (S/cm)                                                      ______________________________________                                        0.0005            5.3 × 10.sup.-5                                       0.002             2.6 × 10.sup.-2                                       0.005             1.9 × 10.sup.-2                                       0.01              1.2 × 10.sup.-3                                       0.02              8.0 × 10.sup.-5                                       ______________________________________                                        *PPTV content was 20%.                                                    

                  TABLE 8                                                         ______________________________________                                        Conductivity of PTV/PE--FeCl.sub.3 Films *                                    PPTV Content (%)                                                                             Conductivity (S/cm)                                            ______________________________________                                         1             1.0 × 10.sup.-9                                           3             4.5 × 10.sup.-7                                           5             8.4 × 10.sup.-7                                          10             4.9 × 10.sup.-6                                          15             3.7 × 10.sup.-4                                          20             1.0 × 10.sup.-2                                          30             8.2 × 10.sup.-2                                          50             3.8 × 10.sup.-1                                          ______________________________________                                        * The PTV/PE--FeCl.sub.3 microfibers were prepared in 0.002 M FeCl.sub.3       --CH.sub.3 NO.sub.2 solution.                                            

                  TABLE 9                                                         ______________________________________                                        Mechanical Properties of PTV/PE--FeCl.sub.3 Films                             PPTV Content                                                                             Young's Modulus                                                                             Tenacity  Elongation                                 (%)        (GPa)         (GPa)     (%)                                        ______________________________________                                         1         0.55          0.36      124                                         5         0.48          0.27      163                                        10         0.35          0.23      151                                        50         0.62          0.12      136                                        ______________________________________                                    

Example 8

The PTV/PE--FeCl₃ fibrils (prepared by doping PTV/PE in 0.1M FeCl₃ --CH₃NO₂ solution) can be blended with PE. The blends were prepared by mixingand hot-pressing a weighed amount of the compressed microfiber films orof the microfibers with PE film at 160° C. four times, each 2 minutes.The films thus obtained were 50-130 mm thick and were strong, flexibleand opaque with a purple or black color, depending on the PTV content.

The electrical conductivity of the PTV/PE--FeCl₃ fibrils mixed andblended with PE are summarized in Table 10. Note that since the PTVcontent in the microfibrils was only 20%, there was finite conductivity(for example, 5×10⁻⁵ S/cm at a concentration of less than 5 wt % PTV.

                  TABLE 10                                                        ______________________________________                                        Conductivity of Blends of PTV/PE--FeCl.sub.3                                  fibrils* with PE                                                              PTV/PE--FeCl.sub.3 Content (%)                                                                    Conductivity (S/cm)                                       ______________________________________                                        10.1                 2.3 × 10.sup.-10                                   20.0                5.0 × 10.sup.-9                                     24.2                5.3 × 10.sup.-5                                     40.1                3.0 × 10.sup.-4                                     60.0                1.4 × 10.sup.-3                                     77.5                1.2 × 10.sup.-2                                     100.0               6.6 × 10.sup.-2                                     ______________________________________                                        *PPTV content was 20%.                                                    

The data of Table 10 are plotted graphically in FIG. 4

Example 9

The PTV/PE--FeCl₃ microfibers prepared directly as in Example 7 canbeblended with PE. After mixing and hot-pressing a weighed amount of themicrofiber material with PE film at 160° C., the resulting electricalconductivities were as listed in Table 11.

                  TABLE 11                                                        ______________________________________                                        Conductivity of Blends of PTV/PE--FeCl.sub.3 *                                Microfibers with PE                                                           PTV/PE--FeCl.sub.3 Content (%)                                                                    Conductivity (S/cm)                                       ______________________________________                                        10.5                3.0 × 10.sup.-12                                    20.8                6.0 × 10.sup.-10                                    26.7                9.1 × 10.sup.-6                                     40.5                1.1 × 10.sup.-4                                     60.8                2.2 × 10.sup.-4                                     79.7                1.9 × 10.sup.-3                                     100                 3.8 × 10.sup.-2                                     ______________________________________                                        *PPTV content was 20%.                                                    

These data are plotted graphically in FIG. 5. Note that since the PTVcontent in the microfibrils was only 20%, there was finite conductivity(for example, 9.1×10⁻⁶ S/cm at a concentration of only about 5 wt %PTV).

The mechanical properties of the blends of PTV/PE--FeCl₃ microfiberswith PE are summarized in Table 12.

                  TABLE 12                                                        ______________________________________                                        Mechanical Properties of Blends of PTV/PE--FeCl.sub.3                         Microfibers with PE                                                           PTV/PE--FeCl.sub.3 *                                                                      Young's Modulus                                                                            Tenacity  Elongation                                 Content (%) (GPa)        (GPa)     (%)                                        ______________________________________                                        9.9         0.35         0.10      150                                        21.1        0.38         0.10      122                                        25.0        0.30         0.16       93                                        39.8        0.54         0.11      118                                        59.4        0.32         0.10      130                                        81.6        0.33         0.34      246                                        ______________________________________                                        *PPTV content was 25%.                                                    

We claim:
 1. A melt processible electrically conductive polymeradmixture comprising from 0.1 to 99.9 parts by weight of elongate finefibrils comprising electrically conductive conjugated polymer, saidfibrils having an aspect ratio of greater than 5 and a diameter of lessthan 200 μm, and from 99.9 to 0.1 parts by weight of melt processibleinsulating polymer.
 2. The polymer admixture of claim 1 wherein saidfibrils themselves consist essentially of conjugated polymer.
 3. Thepolymer admixture of claim 1 wherein said fibrils themselves comprise ablend of conjugated polymer and nonconjugated fibril-forming polymer. 4.A shaped article formed from the polymer admixture of claim 1.